An AC-type surface discharge plasma display panel has become dominance in plasma display panels (hereinafter simply referred to as a panel). The panel contains a front plate and a back plate oppositely disposed with each other and a plurality of discharge cells therebetween. On a front glass substrate of the front plate, scan electrodes and sustain electrodes—a pair of each electrode forms a display electrode—are arranged in parallel with each other, and over which, a dielectric layer and a protective layer are formed to cover the display electrodes. On the other hand, on a back glass substrate of the back plate, data electrodes are disposed in a parallel arrangement, and over which, a dielectric layer is formed to cover the data electrodes. On the dielectric layer, a plurality of barrier ribs is formed in parallel with the arrays of the data electrodes. A phosphor layer is formed on the dielectric layer and on the side surfaces of the barrier ribs.
The front plate and the back plate are sealed with each other so that the display electrodes are orthogonal to the data electrodes in a discharge space between the two plates. The discharge space is filled with a discharge gas, for example, a gas containing 5% xenon in a ratio of partial pressure. The discharge cells are formed at which display electrodes face data electrodes. In the panel structured above, a gas discharge occurs in each discharge cell and generates ultraviolet light, which excites phosphors for red (R), green (G) and blue (B) to generate visible light of respective colors.
In the typical panel operation, one field is divided into a plurality of sub-fields, which is known as a sub-field method. According to the sub-field method, gradation display on the screen is attained by combination of the sub-fields to be lit. Each sub-field has a initializing period, an address period and a sustain period.
In the initializing period, a initializing discharge occurs in the discharge cells. The initializing discharge generates wall charge on each electrode as a preparation for the following addressing operation. There are two types of initializing operation carried out in the initializing period. One is the operation in which the initializing discharge occurs in all of the discharge cells (hereinafter refers to as an all-cell initializing operation), and the other is the operation in which the initializing discharge occurs only in a cell that had sustain discharge (hereinafter refers to as selective-cell initializing operation).
In the address period, address discharge selectively occurs in a cell to be ON to form the wall charge. In the sustain period successive to the address period, sustain pulses are alternately applied between the scan electrodes and the sustain electrodes. The application of pulses generates a sustain discharge in the cells in which the wall charges have been formed in the previous address discharge and excites the phosphor layer of the cells. Through the process above, image is shown on the panel.
In the sub-field methods, a new driving method is disclosed. According to the disclosure, an effective use of the all-cell initializing operation by the application of voltage with a gradually varying waveform and the selective-cell initializing operation can suppress light-emitting that has no contribution to gradation display and therefore improves contrast ratio. Specifically, all of the discharge cells undergo the all-cell initializing operation in the initializing period of one sub-field. In each initializing period of other sub-fields, only a cell where a sustain discharge occurred undergoes the selective-cell initializing operation. As a result, a discharge cell with no contribution to image display has no light-emitting except for the light-emitting occurred in the all-cell initializing operation. This provides a panel with high-contrast image display (for example, see Japanese Patent Unexamined Publication No. 2000-242224).
In response to the recent trend of a larger panel with higher resolution, a suggestion has been made for the improvement of light-emitting efficiency by increasing partial pressure of xenon. Increase in partial pressure of xenon, however, can invite an unstable discharge, such as a delay in discharge. Unstable operations in the all-cell initializing operation can cause a discharge error—a sustain discharge occurs even in a cell without an address discharge. The operational failure (hereinafter, emitting error) can ruin the quality of image display.